As for a conventional single-phase motor, a size of a slot in which an auxiliary winding is contained is reduced, and an outer circumference of a stator iron core is formed into a polygonal shape. Further, with securing magnetic path of a coreback, a width of hoop material of electromagnetic steel sheets is reduced (refer to Patent Document 1, for example).
Further, another conventional single-phase motor has a notch having a roughly semicircular shape on an outer circumference of a stator, so that noise reduction is carried out without interrupting a main magnetic path of a stator iron core (refer to Patent Document 2, for example).    Patent Document 1: JP11-252841    Patent Document 2: JP2001-268824